Sumo is an ancient form of Japanese wrestling that traces its history over many centuries. It is the national sport of Japan, a contest originally intended as an earthly entertainment to appease the gods of the Shinto religion. Sumo today continues many of the traditions that are rooted in religious observance,
Unlike the familiar forms of Olympic wrestling, each with rules that govern how the competitors may physically engage one another, sumo is a very simple sport. The two wrestlers face one another in the designated ring, the dohyo. The ring is approximately 15 ft (5 m) in diameter. Each competitor wears only a loincloth, and the hair pulled back into a ceremonial top knot. At the start of the match, the first wrestler who touches the floor of the ring with any part of his body other than the soles of his feet or the first wrestler who leaves the ring by any means is disqualified. The most common means of winning a match is to execute a hold using the opponent's loincloth to propel the opponent from the ring. The wrestlers are not permitted to punch, choke, or kick one another. Sumo has only one category for competition, with no distinct weight divisions.
A sumo champion holds an exalted status in Japanese society. Sumo wrestlers are ranked in a strict hierarchy, the banzuke; the grand champion of sumo is a yokozuna, a title that is retained by the champion at the conclusion of the wrestler's professional career. The sumo wrestler training and life-style is of legendary strictness, where the young trainees or less accomplished sumo wrestlers are expected to be subservient to the more experienced wrestlers within their training group until they have achieved a measure of success in competition.
At first appearance, the typical sumo wrestler is the antithesis to a fit, accomplished athlete. Most champion sumo wrestlers weight over 350 1b (155 kg), with large and pronounced stomachs and heavy thighs the physical norm. Success in sumo is an application of the basic laws of physics: the lower the center of gravity of the wrestler and the more powerful the initial drive into the opponent, the more likely the opponent will be knocked out of the ring. Most sumo matches are concluded within 30 seconds. Sumo training is directed to the strengthening of the low back to support the very large body mass of the athlete and to facilitate the short two- to three-step explosive burst made by the wrestler at the start of the match to engage the opponent.